1. Technical Field
The present invention relates to gas turbine engines and, in particular, to a duct blocker with rotatable vane segments for regulating fluid flow through a gas turbine engine duct.
2. Background Information
A gas turbine engine may include a bypass flow duct that provides cooling air to one or more engine sections. In one gas turbine engine configuration, for example, the bypass flow duct directs cooling air to an engine combustor section, an engine turbine section and an engine nozzle section. The cooling air is typically bled from a central gas path at a location within an engine fan section or an engine compressor section. Bleeding cooling air from the central gas path, however, may reduce overall engine performance since the cooling air is not utilized to produce thrust. A typical gas turbine engine therefore may include a duct blocker within the bypass flow duct to regulate the quantity of cooling air provided to, for example, the nozzle section in order to increase overall engine performance.
A typical duct blocker includes a duct blocker stator and a duct blocker rotor. The duct blocker stator includes a plurality of leading edge vane segments and a plurality of trailing edge vane segments. The leading edge vane segments and the trailing edge vane segments are respectively circumferentially aligned, and define a plurality of duct blocker airfoil vanes and a plurality of cooling air passages. The duct blocker rotor includes an annular plate that is arranged axially between the leading edge vane segments and the trailing edge vane segments. The annular plate includes a plurality of circumferentially arranged airflow apertures.
During operation, the annular plate slideably rotates around a track, relative to the first and the second vane segments, to regulate the quantity of cooling air flowing through the duct blocker. In an open configuration, the airfoil apertures are circumferentially aligned with the cooling air passages, which permits the cooling air to flow unobstructed through the passages. In a closed configuration, the airfoil apertures are circumferentially aligned with the first and second vane segments, which restricts or prevents the cooling air from flowing through the cooling air passages. Thermal deflection of and hysteresis in the annular plate, however, may reduce precision control of how much cooling air flows through the duct blocker and, thus, may reduce the stability and performance of the engine.